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		<meta charset="UTF-8" />
		<title>Document</title>
		<link rel="stylesheet" type="text/css" href="css/index.css"/>
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		<div class="container">
			<h1 class="display-4">Hell,你好！</h1>
			<p class="lead">This is a simple hero unit, a simple jumbotron-style component for calling extra attention to featured content or information.</p>
			<hr class="my-4">
			<p>It uses utility classes for typography and spacing to space content out within the larger container.</p>
			<a  type="button" class="btn btn-secondary" style="margin-bottom: 20px;">Learn more</a>
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		<div class="container" style="text-align: center;">
			<div class="row">
				<div class="col-md-4 col-sm-12">
					<div class="o">这是第一列</div>
				</div>
				<div class="col-md-4 col-sm-12">
					<div class="o">这是第二列</div>
				</div>
				<div class="col-md-4 col-sm-12">
					<div class="o">这是第三列</div>
				</div>
			</div>
		</div>
		<div class="container" style="text-align: center;">
			<div class="row">
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
				<div class="col-md-1 col-sm-2 col-3"><div class="o">十二栏布局</div></div>
			</div>
			<div class="row">
				<div class="col-md-4 col-12"><div class="o">三栏布局</div></div>
				<div class="col-md-4 col-12">
				<div class="row">
					<div class="col-md-6 col-6"><div class="f">嵌套1</div></div>
					<div class="col-md-6 col-6"><div class="f">嵌套2</div></div>
					<div class="col-md-6 col-6"><div class="f">嵌套3</div></div>
					<div class="col-md-6 col-6"><div class="f">嵌套4</div></div>
				</div>
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				<div class="col-md-4 col-12"><div class="o">三栏布局</div></div>
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